Radio frequency (RF) devices are used in many different types of communication applications. For example, RF devices can be used in cellular telephones with wireless communication components such as switches, MOSFETs, transistors and diodes.
As cellular telephones become more complex and commoditized, there is an increasing need to provide higher performance and lower price points for the wireless communication components. A significant fraction of the cost of manufacturing an RF switch, for example, is the cost to engineer very high linearity such that harmonic distortion is extremely low and meets product specifications.
RF devices are typically manufactured on high resistivity silicon wafers or substrates to achieve the needed rf linearity. State-of-the-art trap rich silicon on insulator (SOI) high resistivity substrates offer excellent vertical isolation and linearity, but the SOI wafer can be up to 50% of the total manufacturing cost because they can be 5 to 10 times the cost of high resistivity non-SOI substrates, i.e., a rf device formed on a SOI wafer could have a total normalized manufacturing cost of 1.0 while a similar device formed on a high resistivity non-SOI bulk wafer could have a total normalized manufacturing cost of 0.6. Devices built on bulk Si substrates have been known to suffer from degraded linearity, harmonics, noise, and leakage currents, any of which will degrade device performance thus necessitating the higher cost of SOI wafers.